Expose component for <base> tag

[gjacobrobertson]

I'm in a similar situation as @maparent in #102. Managing a <base> tag would be useful when when situating an app within a dynamic path. I also considered exposing the HeadTag component directly, but according to MDN, the only head tags not currently supported are <base>, <script>, <noscript>, and <template>, and if you're trying to use react to manage <script>, <noscript> , or <template> tags, you've probably got bigger issues.

So here's a PR that exposes <base> tags as a <Base> component, complete with documentation, example, and typings.

[tizmagik]

Thanks @gjacobrobertson this looks great! I'm not sure why travis didn't run, I'll look into that as soon as I get a chance. Sorry for the lag time and thank you for your patience and contribution!

[tizmagik]

Released in v3.4.0